Method for the removal and recovery of metals and precious metals from substrates

ABSTRACT

A method for removing metal and/or precious metal-containing depositions from substrates, wherein said substrate is subjected to treatment with an organo amine protectant component P and an inorganic active component A. Component P may be formed in situ by reaction with component R. Component P is an organic amine and/or organic amine hydrochloride (preferably diisopropylamine hydrochloride), component A is an inorganic compound (preferably inorganic acid or a mixture thereof) and component R is an organic compound that can be split along the C—N bond by the component A into an organic amine (preferably dimethylformamide or N-methyl pyrrolidone). The metals in the form of organo-metallic complexes can be isolated and/or separated by means of different chemical reactions (preferably reduction reactions) and/or biosorption (preferably with seaweed or yeast).

FIELD OF THE INVENTION

Traditionally it has been a challenge to remove thick and or multiplelayers of depositions of metals and precious metals from various typesof substrates. Current methods typically involve manually ormechanically removing depositions, including precious metal layers,which can damage substrates. Other methods can include the use ofaggressive or poisonous chemicals to remove the precious metals that canalso damage or destroy the substrate or that may not remove the entiredeposition from the substrate. Therefore, it was desirable to develop achemical method to remove layers of depositions, including preciousmetals, form various types of substrates.

Traditionally, separating different precious metals and metals has beena challenging if not impossible task. This has led to the loss ofprecious metals due to the lack of a viable method to separate then oncethey have been chemically changed from a metal to a compound insolution. Therefore, it was desirable to develop a chemical method toselectively remove metals and precious metals from a solution. Selectivebiomass sorption of metals and precious metals has been studied in theprior art. Hydrometallurgy 2010, 103, 180-189. Nilanjana, D.; Recoveryof Precious Metals Through Biosorption, deals with biosorption inrecovery of precious metals from aqueous solutions. The metal bindingmechanism, as well as the parameters influencing the uptake of preciousmetals and isotherm modeling, is presented. Biotechnology Advances 2007,25, 264-271, Mack, C.: Wilhelmi, B. Duncan, J. R., Burgess, J. E.;Biosorption of Precious Metals, reviews recent research regarding thebiosorption of some precious metals, with emphasis on the effects of thebiosorption environment and the biosorption mechanism identified.Biotechnology Advances 2006, 24, 427-451. Wang, J., Chen, C.;Biosorption of Heavy Metals by Saccharomyces cerevisae: A Review,elucidates the mechanism of metal uptake. Various mechanism assumptionsof metal uptake by S. cerevisiae are summarized. Kvasinky, Bachelor'sthesis, Marketa Novakova, 2010, deals with Saccharomyces cerevisiae, andsummarizes cell biological study, and its genome, reproduction, growthconditions, and metabolism.

STATEMENT OF THE INVENTION

This invention concerns use of organo amines, to protect a substratefrom damage during the removal of a deposition consisting of one or morelayers of metal and/or precious metals adhered to the substrate. Once insolution, it is disclosed in this invention to use certain types ofreduction methods and/or biomass materials to extract and separate thedifferent types of metals and/or precious metals. The use of inorganicnitrogen compounds is also contemplated for use with the presentinvention.

The invention provides a method to remove depositions, including metalsand precious metals such as gold and/or platinum and/or titanium, from asubstrate without damaging the substrate and/or efficiently extract itfrom different substrates.

The invention would be a suitable replacement for aqua regia, a knownpowerful acid traditionally used to recovery gold and platinum.Additionally, the invention provides a method for theremoval/extraction/separation of metals and precious metals fromdifferent abrasive blasting media and from solutions of mixtures ofmetals and precious metals, from ores, and from other sources.

The invention will allow for the recovery of gold, platinum and othermetals and precious metals utilizing a chemical method of stripping,separation, and purification from different substrates that results inhigh yields and purity while preserving the substrates. The inventionmay be used either in a batch process for treatment of discretematerials with coatings or in a continuous process for materials in longrolls. The invention has the potential to offer “green technology” byallowing the recovery and recycling of substrates, especially polymericsubstrates that are normally destroyed when recovering precious metalsand by avoiding the use of poisonous chemicals (cyanides for instance)while extracting gold and platinum from ores.

The invention consists of two chemical constituents: a PROTECTANT “P”and an ACTIVE chemical “A” that function to remove a layer and/ormultiple layers of depositions, including metals and/or precious metals,from various types of substrates while not damaging the substrate.PROTECTANT agent “P” functions in the reaction as a surface protectantfor the substrate. Additionally, PROTECTANT agent “P” can function as aCOMPLEXING agent “C” with metals that are oxidized and/or form othermetal compounds. The PROTECTANT agent “P” may be added to the reactiondirectly or created in situ by the chemical reaction between REAGENT “R”and the ACTIVE chemical “A”. Since the PROTECTANT agent “P” protects thesurface of the substrate, it allows the ACTIVE chemical “A” to be achemical or mixture of chemicals (such as aqua regia) that wouldotherwise damage the substrate while dissolving or separating theprecious metals from the substrate.

It has turned out that the protectant function according to theinvention is best performed by mono-, di- and tri-substituted aminesand/or their hydrochlorides, wherein each substituent is independentlyan alkyl or a cycloalkyl. The term “alkyl” as used herein means analiphatic linear or branched group having 1 to 18 carbon atoms. The term“cycloalkyl” herein means a cyclic aliphatic group having 3 to 8 carbonatoms.

Examples of surface PROTECTANT “P”/COMPLEXING agent “C” chemical includethe organo-amines such as trimethylamine hydrochloride ((CH₃)₃N.HCl),dimethylamine hydrochloride ((CH₃)₂NH.HCl), methylamine hydrochloride(CH₃NH₂.HCl), triethylamine hydrochloride ((CH₃CH₂)₃N.HCl),dimethylamine hydrochloride ((CH₃CH₂)₂NH.HCl), methylamine hydrochloride(CH₃CH₂NH₂.HCl), cyclohexylamine hydrochloride (C₆H₁₁NH₂.HCl),dicyclohexylamine hydrochloride ((C₆H₁₁)₂NH.HCl),N,N-dimethylcyclohexylamine hydrochloride (C₆H₁₁N(CH₃)₂.HCl),diisopropylamine hydrochloride ((CH₃)₂CHNHCH(CH₃)₂.HCl),N-ethylcyclohexylamine hydrochloride (C₆H₁₁NC₂H₅.HCl),N-methylcyclohexylamine hydrochloride (C₆H₁₁NCH₃.HCl), etc.

Examples of REACTIVE “R” surface protectant/COMPLEXING “C” agents thatcan form amines in situ include dimethylformamide (DMF)-C₃H₇NO) andN-methyl pyrrolidone (NMP)-C₅H₉NO, and other organic compounds (such asamides and/or lactams) that can be split along the C—N bond into anamine and other organic compound (such as dimethylamine and formic acidin case of DMF).

Examples of ACTIVE chemical “A” include inorganic acids and mixturesthereof from the group consisting of nitric acid (HNO₃) and/orhydrofluoric acid (HF), and/or hydrochloric acid (HCl) and/or phosphoricacid (H₃PO₄), and/or fluorosilicic acid (H₂SiF₆), and/or ammoniumperoxydisulfate ((NH₄)₂S₂O₈), and/or sulfuric acid (H₂SO₄), and otherinorganic compounds that can cause splitting organic compounds (such asamides and/or lactams) along the C—N bond into organic amine(s) andother organic compounds and/or can dissociate any amine hydrochlorideinto the PROTECTANT “P” and COMPLEXING agent “C” to allow its dualaction (protecting and complexing).

Examples of substrates include aluminum, copper, steel, stainless steel,glass, titanium, their alloys, graphite, carbon fibre, ceramic, fusedsilica, quartz, blasting media (such as corundum, sand, corn cob,plastic abrasives, silicon carbide, pumice, steel grit, steel shot,walnut shells, soda, and glass beads), polymers (such as PEEK, PET,polyimide, polyether, etc.) and ores.

The following equations illustrate the two chemical reaction mechanisms:

[Deposition on Substrate]+P/C+A→Deposition (in solution) or Deposition-C(in solution)+Substrate-P+Solution

[Deposition on Substrate]+R/C+A→Deposition (in solution) or Deposition-C(in solution)+Substrate-P+Solution

where Deposition=one or more selected from Be, Mg, Ca, Ti, Zr, V, Nb,Ta, Cr, Mo, W, Mn, Fe, Ni, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, In,Tl, C, Si, Sn, N, P, As, S, Se, Te, and their mixtures, and/or theirchemical compounds.

Once the depositions have been separated from the substrate anddissolved and/or extracted into solution, separating the differentprecious metals has traditionally been a challenging if not impossibletask. One method to remove metals from solution is the use of biomassmaterials to selectively biosorb reaction products that were originatedin situ by chemical reactions between the deposition and/or “P” and/or“R” and/or “A”. The use of biomass materials allows one to reclaimmetals and/or precious metals that would have otherwise been difficultand/or unsafe to separate. Specifically, certain types of biomassmaterials are able to bind and concentrate metals from aqueoussolutions. A biosorption-based process offers a number of advantagesincluding low cost, selective metal reclamation, high efficiency inmetal complexation and high purity of the final metal.

This invention consists of using selected biosorbants to recover metalsand/or precious metals and/or their chemical compounds. Examples ofselective biosorbants include seaweed (ie Spirulina platensis) and yeast(i.e. Saccharomyces cerevisiae).

The following equations illustrate the selective chemical reactionmechanisms:

[Mixture of M's (X,Y,Z)] (in solution)+Bioadsorbant (I)->[M(X)+Bioadsorbant]+[Mixture of M's (Y,Z)] (in solution

[Mixture of M (X,Y,Z)] (in solution)+Bioadsorbant (II)->[M(Y)+Bioadsorbant]+[Mixture of M's (X,Z)] (in solution)

where M=Metals and/or Precious Metals and/or their chemical compounds

-   X,Y,Z=Mixture of Metals and/or Precious Metals and/or their chemical    compounds

The following FIGURES and EXAMPLES illustrate the invention.

BRIEF DESCRIPTION OF FIGURES

FIG. 1 depicts an apparatus for recovering gold from a PET substrate.The PET substrate is provided in spooled rolls. As shown in FIG. 2, thegold-hued PET is fed from the roll to a first station where it is soakedin a cleaning solution that was made in accordance with the teachings ofthe present invention. See FIG. 3. In FIG. 4, the substrate is passedfrom the first station to a second station that is filled with water. Bypassing the substrate through the second station, the majority of thesolution from the first station is removed. In FIG. 5, the substrate ispassed through a series of rollers to remove the rest of the cleaningsolution and subsequently passed through a water mist. The liquids fromall stations are subjected to a gold recovery process includingreduction. As illustrated in FIG. 6, the illustrated rolls are 425meters long and two such rolls can be processed in approximately 90minutes in the illustrated continuous process. As shown in FIG. 7,approximately 187 g of gold are recovered for every 100 kg of the PETsubstrate.

FIG. 8 illustrates a batch process for cleaning a substrate andrecovering the gold plating. Gold-plated substrates are soaked in acleaning solution that was made in accordance with the teachings of thepresent invention. Before submersions, the sheets have a metallic hue.As shown in FIG. 9, after briefly soaking the substrate, the metallichue is gone and the substrate is white. FIG. 10 provides a depiction ofone submerged substrate (white) and one pre-treated substrate(metallic). As shown in FIG. 11, after soaking, the residual cleaningsolution is removed from the substrate by rising with water. FIG. 12depicts the cleaned, white substrate. The gold layer was removed withoutdamaging the substrate, including notes that were written on thesubstrate. FIG. 13 provides another depiction of the metallic substrateprior to treatment.

FIG. 14 depicts an aqua regia solution dissolving a copper substrate.The copper wire gets dissolved within 40 minutes. FIG. 15 illustratesthe addition of DMF to the aqua regia solution and the subsequentinability of the DMF solution to rapidly dissolve the copper wire (FIG.16). The copper wire stays intact long enough until the aqua regiadissolves a possible deposition.

FIG. 17 depicts a copper part plated with gold, platinum and titanium.After two days of soaking in the inventive cleaning solution followed bybrush cleaning, the majority of the metal layer was removed withoutdamaging the copper. See FIGS. 18 and 19. The copper part is intact,i.e. the aqua regia selectively etched the deposition only, while DMFserved as surface protectant.

FIG. 20 depicts an aluminum part plated with SiOx deposits. In order toetch the SiO_(x) the aluminum part was treated with DMF and a mixture ofphosphoric acid and hydrofluoric acid (where the organo-amine is formedin-situ). A layer of black material was visible (FIG. 21) on the surfaceof the aluminum which was rinsed away with water. FIG. 22 depicts thealuminum part undamaged from this treatment method. Without wishing tobe bound to any particular theory, applicant believes this blackmaterial is a protective layer that prevents damage to the aluminumpart.

FIGS. 23 through 27 depict that a multilayer deposition of gold,platinum, titanium, and aluminum has been dissolved and removed from astainless steel substrate using an organo-amine and nitric acid. FIG. 23depicts parts feeding into the reaction mixture (etching solution). Theratio of chemicals stays the same every time a fresh solution isprepared. All 4 of the metals were successfully dissolved/removed fromthe stainless steel substrate without damage to the substrate (FIG. 27).Subsequently, the gold was separated from the platinum, titanium, andaluminum using gold reduction methods (FIG. 28; addition of the reducingagent; FIG. 29; filtration of the solution with gold powder; FIG. 30;cleaning the melted gold's surface from residues), and purified to99.99% minimum purity (FIG. 31). Likewise, the platinum was separatedfrom the titanium/aluminum solution using a biosorption method (forexample, using yeast, FIGS. 32 through 34).

EXAMPLES Example 1—Comparative

A sample of nitric acid (50%) and hydrochloric acid (31%) was prepared(1:1 volume ratio). Several pieces of copper wire were added to thissolution. The copper wire completely dissolved within 40 minutes.

Example 2

A 20 mL sample of nitric acid (50%) and 20 mL hydrochloric acid (31%)was prepared in 200 mL N,N-dimethylformamide (DMF). Several pieces ofcopper wire were added to this solution. The copper wire showed no signsof dissolving within 40 minutes.

Example 3

A sample of 100 mL nitric acid (50%) and 300 mL hydrochloric acid (31%)was prepared in 4 L N,N-dimethylformamide (DMF). A solid piece of copperwas coated with an alloy of gold, platinum and titanium. The copper wassoaked in the sample solution for fourteen days at room temperature. Thecopper was removed from the solution and rinsed and manually washed toremove residual protective coating. The resulting copper appeared freeof gold, platinum and titanium. There was no visible damage to thecopper.

Example 4—Comparative

A sample of phosphoric acid (50%) and hydrofluoric acid (50%) wasprepared. A piece of aluminum foil was added to this solution. Thealuminum completely dissolved within 20 minutes.

Example 5

A sample of 25 mL phosphoric acid (50%) and 25 mL hydrofluoric acid(50%) was prepared in 400 mL N,N-dimethylformamide (DMF). A piece ofaluminum foil was added to this solution. The aluminum showed no signsof dissolving within 20 minutes.

Example 6

A sample of 30 L phosphoric acid (50%) and 30 L hydrofluoric acid (50%)was prepared in 200 L N,N-dimethylformamide (DMF). A sheet of aluminumwas coated with a SiOx deposition. The aluminum was soaked in the samplesolution for ten days at room temperature. The aluminum was removed fromthe solution and rinsed and manually washed to remove residualprotective coating. The resulting aluminum appeared free of the SiOxdeposits. There was no visible damage to the aluminum.

Example 7

A gold-coated polyethylene terephthalate (PET) substrate (57.6 kg) wasprovided as a rolled thin-film. The film was sequentially rolled throughthe solution 50 L of nitric acid (50% diluted) and 3.5 kg oftrimethylamine hydrochloride at a rate of about 9 meters per minute. Thefilm was rinsed under a stream of water to remove trace acid. Afterprocessing, the gold-color was no longer visible on the film and thecleaning agents were gold-colored. There was no visible damage to thePET substrate.

Example 8

A provided stainless steel substrate coated with gold, platinum,titanium and aluminum (44 parts of different weights and sizes) wassubmerged into an etching mixture of 240 L of nitric acid (50%) and 16kg of trimethylamine hydrochloride. All layers of gold, platinum,titanium, and aluminum dissolved in the etching mixture within 3 hoursto 30 days depending on the thickness of the layers. There was novisible damage to the stainless steel parts. The solution wassubsequently subjected to a reduction and refinement process thatseparated the gold from the other metals and refined the gold to 99.99%minimum purity. To the remaining solution containing platinum, titanium,and aluminum yeast (Saccharomyces cerevisiae) was added in the ratio of1 kg of yeast per 200 liters of the solution. The organo-platinumcomplex was left to selectively bioadsorb onto the yeast for one day tosuccessfully separate the platinum from the other metals. Thenyeast/organo-platinum complex mix was then filtered off and burned at1500° C. The remaining platinum oxide was isolated, pressed intopellets, and vacuum melted into platinum metal.

Example 9

The gold containing solutions of example 7 and 8 were subjected to areduction and refinement protocol to provide 99.99% minimum puritygold—107.75g of gold (187 g Au per 100 kg of the PET strip). Thefollowing describes the reduction and refinement protocol.

Example 10—Comparative

Three pieces of gold of similar shape, each 30 grams, were submergedinto three etching mixtures. Each mixture consisted of 15 liters ofnitric acid (50%) and (1) 1 kg of trimethylamine hydrochloride, (2) 1 kgof dimethylamine hydrochloride, (3) 1 kg of methylamine hydrochloride.The speed of gold dissolutions were measured over the period of twoweeks and compared. The experiments suggested that the aminehydrochloride ability to dissolve and/or etch gold decreases in thetrimethylamine hydrochloride>dimethylamine hydrochloride>methylaminehydrochloride order. The speeds were: 0.81 g>0.65 g>0.52 g of goldweight loss per day (room temperature, no stirring).

Example 11—Comparative

Five pieces of gold of similar shape, each 30 grams, were submerged intofive etching mixtures. Each mixture consisted of 15 liters of nitricacid (50%) and (1) 1 kg of triethylamine hydrochloride, (2) 1 kg ofdiisopropylamine hydrochloride, (3) 1 kg of N-ethylcyclohexylaminehydrochloride, (4) 1 kg of dibutylamine hydrochloride and (5) 1 kg oftrimethylamine hydrochloride. The speed of gold dissolutions weremeasured over the period of two weeks and compared. The experimentssuggested that the amine hydrochloride ability to dissolve and/or etchgold decreases in the diisopropylamine hydrochloride>dibutylaminehydrochloride>triethylamine hydrochloride>N-ethylcyclohexylaminehydrochloride>trimethylamine hydrochloride order. The speeds were: 2.03g>1.78 g>1.53 g>1.51 g>0.81 g of gold weight loss per day (roomtemperature, no stirring).

Example 12—Comparative

Two pieces of gold of similar shape, each 30 grams, were submerged intotwo etching mixtures. Each mixture consisted of 15 liters of nitric acid(50%) and (1) 1 kg of N-ethylcyclohexylamine hydrochloride, purchasedcommercially, and (2) 1 kg of N-ethylcyclohexylamine hydrochloride,prepared in situ by mixing appropriate amounts of N-ethylcyclohexylamineand hydrochloric acid, followed by adding the nitric acid. The speed ofgold dissolutions were measured over the period of two weeks andcompared. The speeds were: 1.51 g/1.50 g per day (room temperature, nostirring). The experiments suggested that there is no difference inability to dissolve and/or etch gold between the commercial and in situprepared chemical.

Reduction and Refinement of Gold Recovered from a Substrate

Once the gold has been removed from a substrate and is in solution as acomplex, it must then be reduced through chemical treatment to formelemental gold.

Reduction of the gold is accomplished as follows. Dilute the goldsolution with between 60% to 80% by volume of the solution withdistilled water. Then add a saturated aqueous solution of urea(H₂NCONH₂) to the diluted solution of gold (5 kg per 250 liters ofsolution) to destroy the nitric acid, HNO₃. Neutralization of thesolution is determined by standard methods such as pH, titration,visual, or by other methods. Once the solution has been neutralized,hydroxylamine hydrochloride, NH₂OH.HCl, is added to the solution at roomtemperature. Addition of the hydroxylamine hydrochloride is done in 5 kgquantities until all of the gold has been precipitated from solution.Likewise, the hydroxylamine hydrochloride is added in 5 kg quantities soas to avoid any hazards in adding too much of the reducing agent tooquickly. The presence of gold in the solution is tested on a smallsample of solution using tin chloride, SnCl₂. If gold is still present,a dark brown/black precipitate will form with the addition of tinchloride. If no gold is present, the color of the solution will stay thesame and be free of precipitate. Once all of the gold has beenprecipitated from solution, most of the solution is decanted from thegold precipitate, the gold is then filtered through a standard filterpaper, and rinsed with distilled water during filtration. The recoveredgold powder and filter paper are dried at 120-130 C for 4 hours in astandard convection oven. The gold powder is weighed after it is fullydried, and all gold is removed from the filter paper, using a wire brushif necessary to get as much gold as possible from the paper. The goldpowder is now transferred to a melting crucible, mixed with anhydroussodium tetraborate (Na₂B₄O₇), two teaspoons of borax per 200 grams ofgold powder, and heated to 1180° C. for 5 to 10 minutes. The crucible iscooled in water and destroyed so as to remove the gold. The recoveredgold “Roundlet” is boiled in nitric acid (12M, diluted by 50%, 2 hoursminimum), rinsed with distilled water, air dried, weighed, rinsed withisopropyl alcohol, and air dried a final. The gold is now 99.99% minimumpurity.

1. A method for removing metal and/or precious metal-containingdepositions from substrates, wherein said substrate is subjected totreatment with an organo amine protectant component “P”/complexingcomponent “C” and an inorganic active component “A”, wherein saidcomponent “P”/“C” is selected from the group including mono-, di- andtri-substituted amine hydrochlorides, wherein each substituent isindependently an alkyl having 1 to 18 carbon atoms or a cycloalkylhaving 3 to 8 carbon atoms, and wherein said component “A” is aninorganic acid or its salt or a mixture thereof.
 2. The method of claim1, wherein said organo amine protectant is prepared in situ by reactionof organic amine and hydrochloric acid.
 3. The method of claim 1,wherein said component “P” is selected from triethylamine hydrochloride,diethylamine hydrochloride, ethylamine hydrochloride, dicyclohexylaminehydrochloride, N,N-dimethylcyclohexylamine hydrochloride,diisopropylamine hydrochloride, N-ethylcyclohexylamine hydrochloride andN-methylcyclohexylamine hydrochloride.
 4. The method of claim 1, whereinsaid component “P” is selected from trimethylamine hydrochloride,dimethylamine hydrochloride and methylamine hydrochloride.
 5. The methodof claim 1, wherein said component “P”/“C” is formed in situ by reactionof said component “A” with a reactive component “R”.
 6. The method ofclaim 5, wherein said component “R” is selected from the group oforganic amides and/or organic lactams.
 7. The method of claim 6, whereinsaid component “R” is selected from dimethylformamide and N-methylpyrrolidone.
 8. The method of claim 1, wherein said component “A” isaqua regia.
 9. The method of claim 1, wherein said component A isselected from the group including nitric acid, hydrofluoric acid,hydrochloric acid, phosphoric acid, hexafluorosilicic acid, ammoniumperoxydisulfate and sulfuric acid and mixtures thereof.
 10. The methodof claim 1, wherein said deposition comprises at least one selected fromthe group including Be, Mg, Ca, Ti, Zr, V, Nb, Ta, Cr, Mo, W, Mn, Fe,Ni, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, In, Tl, C, Si, Sn, N, P, As,S, Se, Te, and their mixtures, and/or their chemical compounds.
 11. Themethod of claim 1, wherein said substrate comprises at least oneselected from the group including aluminum, copper, steel, stainlesssteel, glass, titanium, their alloys, graphite, carbon fibre, ceramic,fused silica, quartz, blasting media (such as corundum, sand, corn cob,plastic abrasives, silicon carbide, pumice, steel grit, steel shot,walnut shells, soda, and glass beads), polymers and ores.
 12. The methodof claim 1, wherein said metal(s) is (are) recovered from theorgano-metallic complex(es) in the solution resulting from saidtreatment.
 13. The method of claim 12, wherein said recovery is carriedout by means of a biosorbant.
 14. The method of claim 13, wherein saidbiosorbant is selected from seaweed and yeast.
 15. The method of claim14, wherein the biosorbant is Spirulina platensis.
 16. The method ofclaim 15, wherein the biosorbant is Saccharomyces cerevisiae.
 17. Aprocess for obtaining gold and/or platinum from a solution resultingfrom treatment of a substrate with depositions of gold, platinum andoptionally other metals by the method of claim 1, said processcomprising the following steps: (a) subjecting the solution resultingfrom said treatment, which contains organo-metallic complexes of therespective metals, to a reduction and refinement process to separate thegold from the complexes and/or other chemical compounds of the othermetal(s), (b) adding yeast to the remaining solution in order toselectively biosorb the organo-platinum complex, (c) isolating theresulting yeast/organo-platinum complex by filtration and burning it toobtain platinum oxide, and (d) reducing the platinum oxide to platinummetal.
 18. The method of claim 17, wherein the substrate comprises atleast one selected from the group including aluminum, copper, steel,stainless steel, glass, titanium, their alloys, graphite, carbon fibre,ceramic, fused silica, quartz, blasting media (such as corundum, sand,corn cob, plastic abrasives, silicon carbide, pumice, steel grit, steelshot, walnut shells, soda, glass beads, polymers and ores.